Solder flow stops for semiconductor die substrates

Abstract

A substrate, which has semiconductor die arranged thereon, uses at least one solder flow stop, closely surrounding at least a portion of at least one mounting pad on which the die are mounted, to prevent die rotation during solder reflow. The at least one solder stop is non-wetting, during a solder reflow process, to solder used to mount the die.

1. A substrate having at least one conductive mounting pad on which at least one die is mountable by soldering, said mounting pad having at least one solder flow stop around at least a portion of its periphery and being relatively closely spaced from the periphery of said mounting pad; wherein said substrate comprises a dielectric layer formed on a base layer and a circuit layer formed on said dielectric layer, a portion of said circuit layer comprising said at least one conductive mounting pad, and wherein said flow stop includes an upper surface level with an upper surface of said circuit layer, wherein said conductive mounting pad is comprised of a first metallic body and said solder flow stop is comprised of a second metallic body different from said first metallic body and non-wetting, during a solder reflow process, to a solder which is usable for mounting the at least one die on said at least one conductive mounting pad. 
     
     
       2. The substrate of  claim 1 , wherein the at least one solder flow stop is made of aluminum. 
     
     
       3. The substrate of  claim 1 , wherein the at least one solder flow stop is aluminum and has a bond pad area extending therefrom. 
     
     
       4. The substrate of  claim 3 , wherein the solder used is made of tin-lead. 
     
     
       5. The substrate of  claim 1 , wherein the at least one solder flow stop surrounds at least a portion of the circuit layer. 
     
     
       6. The substrate of  claim 1 , wherein there is a gap between the at least one solder flow stop and the circuit layer. 
     
     
       7. The substrate of  claim 1 , wherein the solder used is an alloy selected from the group of alloys consisting of tin-lead, tin-lead-silver, tin-antimony, lead-indium, tin-lead-indium, tin-bismuth, and tin-lead-bismuth. 
     
     
       8. The substrate of  claim 1 , wherein the substrate is selected from the group of substrates consisting of insulated metal substrate, epoxy-glass substrate, paper phenolic substrate, direct-bond copper, ceramic substrate, silicon substrate, printed circuit board, printed wiring board, and flexible circuit.